Mobile devices such as cellular telephones, smart phones, and other handheld or portable electronic devices such as personal digital assistants (“PDAs”), headsets, MP3 players, etc. have become popular and ubiquitous. As more and more features have been added to mobile devices, there has been an increasing desire to equip these mobile devices with input/output mechanisms that accommodate numerous user commands and/or react to numerous user behaviors. It is of increasing interest that mobile devices be capable of detecting the presence of, and determining with some accuracy the position of, physical objects located outside of the mobile devices and, more particularly, the presence and location of human beings (or portions of their bodies, such as their heads or hands) who are using the mobile devices or otherwise are located nearby the mobile devices. By virtue of such capabilities, the mobile devices are able to adjust their behavior in a variety of manners that are appropriate given the presence (or absence) and location of the human beings and/or other physical objects.
While remote sensing devices such as infrared (or, more accurately, near-infrared) transceivers have been employed in the past in some mobile devices to allow for the detection of the presence and/or location of human beings and/or physical objects even based on their movement, such sensing devices have been limited in various respects. In particular, some such near-infrared transceivers in some such mobile devices are only able to detect the movement of a human being/physical object within a certain distance from the given transceiver, but not able to detect the continuous presence of the human being/physical object after the human being/physical object stops moving or vice versa. Also, some such transceivers in some such mobile devices are undesirably complicated, require large numbers of components in order to operate, or require optical elements that attenuate the received infrared signals, which in turn renders such devices unduly expensive and inefficient.